40 MR. B. GARNER ON THE SHELL-BEARING MOLLUSCA. 



its organs may be seen to be reversely disposed to those of the 

 larger species, the heart being placed to the right, before the apex 

 of the shell, and the rectum also on the same side. 



3. Doris, S^c. — The little Doris aspera swims, back downwards, 

 on the surface of a glass of sea-water, copulates, and deposits its 

 semicircular oothecae. The brain of the common Lemon Doris is 

 of a fine orange eoloiu', enveloped in a glandular matter, and is 

 constituted by a complicated assemblage of ganglia : there are 

 acoustic sacs and dark ocular spots upon it. There are six ganglia 

 on the buccal mass, and about six or eight minute ones on the 

 stomach. The anal sac appears to be a purple- or ink-bag; and 

 the so-called matrix is composed of a peculiar substance, swelling 

 enormously in water, of which it renders a large quantity viscid, 

 and being also coagulable by alcohol and bichloride of mercury, 

 but not by heat. Spermatozoa M-ere found in the genital vesicle, 

 as well as in the epididymis and its caecum. The spines of the 

 lingual plate are uniform, and in number about 10,000. 



4. Apltsia, Sfc. — Aplysia has been before alluded to. Cuvier, 

 in his generally beautiful drawings, has scarcely done justice 

 to (5) lanthina, nor to its beautiful float and ootheca; it is 

 peculiar for its fins, and the disk at the back of the foot. With 

 respect to Magilus, it should be removed from the (6) Tubuli- 

 branchiata, its animal being a Purpura in structure, with a bent 

 horny operculum, and a very long linear appendage on the right 

 side of the head, leading to the supposition that the animals are 

 of difierent sexes, though there seem to be difficidties in the way 

 of sexual congress. In the specimen examined, the spire of the 

 shell was not solidified ; the animal had a short proboscis, with 

 rather bent subulate feelers, and eyes on the outside ; it had also 

 a rich purple secretion near the rectum on the right side. 



7. Trochus, Sfc. — Some of the species of Trochus surpass even 

 Mmargimila in the beauty of their lingual apparatus. The renal 

 organ opens into the bottom of the branchial cavity, contrary to its 

 disposition in Helix and Lymncttis, where its exit is near the respi- 

 ratory orifice. In Flanorhis, that part of the respiratory cavity 

 receiving the excretions seems separated by an imperfect valve 

 from the right portion. With respect to the secretion of this organ, 

 it consists, in both Gasteropoda and Lamellibrauchiata, of niune- 

 rous pellucid globular bodies, containing opaque earthy nuclei or 

 granules, and presenting diftereut appearances in Anodon (for 

 instance), Cyclostoma, Buccinum, and Helix. When these bodies 

 are incinerated, lime is left, which in some cases appears to ha\e 

 been combined with oxalic acid. The little JVerita litoralis presents 



